From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 651E4C4360C for ; Thu, 26 Sep 2019 07:43:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 38AF8222C9 for ; Thu, 26 Sep 2019 07:43:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1569483796; bh=/CtuN6T2j2r0aYMLlRQC2PGu7g33EqBSitWRz4L9GJI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=ZsbxWa563Dg5NN0eZPUeLne3fbaU42THKfxXJreF2r2+H6iOjmu7p7iEyGsOIIp35 1xOEcVGbnAR3QRKmKAXqYzdhemaseS4bWR5ScKwrBIwFD6zZVNt+ITzgJ+dQ6mqMKx h727/HVof0JIrDdiyiy1B4Oi4kvUZVndITpUrDHE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731231AbfIZHnP (ORCPT ); Thu, 26 Sep 2019 03:43:15 -0400 Received: from mx2.suse.de ([195.135.220.15]:38512 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728870AbfIZHnP (ORCPT ); Thu, 26 Sep 2019 03:43:15 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 319C0AE65; Thu, 26 Sep 2019 07:43:13 +0000 (UTC) Date: Thu, 26 Sep 2019 09:43:12 +0200 From: Michal Hocko To: David Hildenbrand Cc: Alastair D'Silva , alastair@d-silva.org, Andrew Morton , Oscar Salvador , Pavel Tatashin , Dan Williams , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4] memory_hotplug: Add a bounds check to __add_pages Message-ID: <20190926074312.GD20255@dhcp22.suse.cz> References: <20190926013406.16133-1-alastair@au1.ibm.com> <20190926013406.16133-2-alastair@au1.ibm.com> <8e00cf16-76b9-6655-86b6-288b454d6fe5@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8e00cf16-76b9-6655-86b6-288b454d6fe5@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 26-09-19 09:12:50, David Hildenbrand wrote: > On 26.09.19 03:34, Alastair D'Silva wrote: > > From: Alastair D'Silva > > > > On PowerPC, the address ranges allocated to OpenCAPI LPC memory > > are allocated from firmware. These address ranges may be higher > > than what older kernels permit, as we increased the maximum > > permissable address in commit 4ffe713b7587 > > ("powerpc/mm: Increase the max addressable memory to 2PB"). It is > > possible that the addressable range may change again in the > > future. > > > > In this scenario, we end up with a bogus section returned from > > __section_nr (see the discussion on the thread "mm: Trigger bug on > > if a section is not found in __section_nr"). > > > > Adding a check here means that we fail early and have an > > opportunity to handle the error gracefully, rather than rumbling > > on and potentially accessing an incorrect section. > > > > Further discussion is also on the thread ("powerpc: Perform a bounds > > check in arch_add_memory") > > http://lkml.kernel.org/r/20190827052047.31547-1-alastair@au1.ibm.com > > > > Signed-off-by: Alastair D'Silva > > --- > > mm/memory_hotplug.c | 20 ++++++++++++++++++++ > > 1 file changed, 20 insertions(+) > > > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > > index c73f09913165..212804c0f7f5 100644 > > --- a/mm/memory_hotplug.c > > +++ b/mm/memory_hotplug.c > > @@ -278,6 +278,22 @@ static int check_pfn_span(unsigned long pfn, unsigned long nr_pages, > > return 0; > > } > > > > +static int check_hotplug_memory_addressable(unsigned long pfn, > > + unsigned long nr_pages) > > +{ > > + unsigned long max_addr = ((pfn + nr_pages) << PAGE_SHIFT) - 1; > > + > > + if (max_addr >> MAX_PHYSMEM_BITS) { > > + WARN(1, > > + "Hotplugged memory exceeds maximum addressable address, range=%#lx-%#lx, maximum=%#lx\n", > > + pfn << PAGE_SHIFT, max_addr, > > + (1ul << (MAX_PHYSMEM_BITS + 1)) - 1); > > + return -E2BIG; > > + } > > + > > + return 0; > > +} > > + > > /* > > * Reasonably generic function for adding memory. It is > > * expected that archs that support memory hotplug will > > @@ -291,6 +307,10 @@ int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages, > > unsigned long nr, start_sec, end_sec; > > struct vmem_altmap *altmap = restrictions->altmap; > > > > + err = check_hotplug_memory_addressable(pfn, nr_pages); > > + if (err) > > + return err; > > + > > if (altmap) { > > /* > > * Validate altmap is within bounds of the total request > > > > > I know Michal suggested this, but I still prefer checking early instead > of when we're knees-deep into adding of memory. What is your concern here? Unwinding the state should be pretty straightfoward from this failure path. -- Michal Hocko SUSE Labs